Earth drilling rigs



Nov. 24, 1964 H. D. FANSHAWE ETAL 2 EARTH DRILLING axes Filed Aug. 4, 1958 1 1 Sheets-Sheet l NOV. 1954 H. D. FANSHAWE ETAL 3,153,212

EARTH DRILLING RIGS File d Aug. 4, 1958 11 sheeis-shee 2 FIGS.

1964 H. D. FANSHAWE ETAL ,1

EARTH DRILLING RIGS Filed Aug. 4, 1958 ll Sheets-Sheet 4 FIG.6

mum... E.

V Xj- Emmi-Emu Nov. 24, 1964 H. D. FANSHAWE ETAL EARTH DRILLING RIGS Filed Aug. 4, 1958 11 Sheets-Sheet 5 59 oi j 58 1964 H. n. FANSHAWE ETAL 3,153,212

EARTH DRILLING RIGS 11 Sheets-Sheet 6 Filed Aug. 4, 1958 v KAI- FI'G.8.

1964 H. D. FANSHAWE ETAL 3,153,212

EARTH DRILLING RIGS Filed Aug. 4, 1958 11 Sheets-Sheet '7 New. 24, 1964 Filed Aug, 4, 1958 H" n. FANSHAWE ETAL 3,158,2I2

mm DRILLING RIGS 1 11 Sheets-Sheet 8 FIEGJQ'KI Nov. 24, 1964 H. D. FANSHAWE ETAL 3,158,212

EARTH DRILLING RIGS Filed Aug. 4, 1958 ll Sheets-Sheet 9 Nov. 24, 1964 H. n. FANSHAWE ETAL EARTH DRILLING RIGS Filed Aug. 4, 1958 ll Sheets-Sheet l0 M. my.

1964 H. D. FANSHAWE ETAL 3,158,212

EARTH DRILLING RIGS Filed Aug. 4, 1958 ll Sheets-Sheet 11 2 3 a FIG l4.

United States Patent 3,158,212 EARTH DRILHNG RIGS ew Dalrymple Eanshawe, Wenddve'r, and William Ed.-

ward Digby, Bil ion, Rugby, England, assignors to National Research Eevelopment Qorporation, London,

Engiand, a British corporation FiledA N 335 Ciaizns priority, applic tion Great Britain, Aug. 9, E57,

25,258/57 21 (Ilaim's; '(Cl."1l75- -85) The present invention relates to earth drilling rigs of the kind used for drilling deep boreholes. The invention is mainly applicable to the drilling of boreholes for oil especially at great depths.

In the drilling of boreholes for oil a great deal of the time is taken up with the processes of extracting pipe from the hole for the purpose of changing the drilling bit and returning the pipe to the hole. The greater the depth, the greater the time lost in carrying out these processes, and the present invention is concerned with the problem of speeding them up. Drill pipe is normally manufactured in lengths of approximately 30 feet, successive lengths being joined by tapered screw unions called tool joints, the male and female members of which are screwed. on to the opposite ends of the pipes. When pulling out pipe therefore, it is necessary as each pipe length is pulled clear of the hole, to unscrew it and remove it, and this involves breaking the tightly screwed up tool joint, unscrewing the upper pipe to disengage the tool joint and setting aside the upper pipe. In order to reduce the time taken up by this process the tendency, has developed for stands. consisting of several lengths of pipe screwed together to be removed as one piece, the drilling rig being made of great enough height to accommodate the multiple pipe length of the stand. Rigs have therefore become more and more unwieldy, and one of the objects of this invention is to provide a more compact rig. Another object of the invention is to provide a rig which will enable considerable lengths of pipe to be pulled continuously, successive sections of pipe being removed as re quired without halting the pulling process. A shorter rig is thus made possible since it does not need to be designed to pull long stands at a time.

Another object ofthe invention is to provide a rig in which these processes are carried out automatically so that the process may proceed smoothly and without interruption.

The invention also enables the advantages of hydraulic pulling apparatus to be enjoyed by virtue of the shorter pull required when pipes are removed one by one.

In co-pending British application No. 29,153/56 there is described a rig in which two lifts are provided, one above the other, each adapted to pull the pipe string in turn so as to maintain a continuous pulling action upon the pipe. The present invention is concerned with developments of the invention described in that earlier specification.

According to the invention in one aspect an earth drilling rig comprises at least two lifts each carrying mechanism adaptcd'to engage a drill pipe and carry out an operation thereon, wherein the'mechanisrn carried 3,158,212 Patented Nov. 24, 1964 on at least one of said lifts comprises two parts adapted to separate to allow the passage between them of pipe engaging means carried by the other of said lifts and to come together to combine into a functional entity to carry out an operation on said drill pipe, whereby the pipe engaging means of the two pipes can pass one another and the lifts may operate over strokes which at least overlap in part.

According to the invention in another aspect an earth drilling rig comprises two lifts each adapted to pull a drill pipe string, both said lifts carrying mechanism adapted to engage the drill pipe string so as to pull same from the bore hole and at least one of them carrying break-out mechanism adapted to engage a drill pipe joint and spinoff mechanism adapted to engage a pipe above the broken joint and spin it off wherein at least part of the mechanism carried on at least one of said lifts is separable into two parts adapted to move apart to allow passage therebetween of the mechanism carried by the other lift.

In the apparatus in one of its forms, which will be described by way of example, the lifting means comprise two pairs of hydraulic rams each pair carrying a lifting platform which in turn carries a pipe gripping and unscrewing mechanism. One pair of. rams straddles the other pair, which in turn straddles the drill hole and the two platforms carried by the rams lie on opposite sides of the central plane in which the rams and the borehole are located. The pipe dismantling means comprises three sections, one of which serves for gripping the pipe for the purposes of pulling the pipe string, one, the breakout section, for breaking the joint prior to unscrewing, and one for spinning oif the end pipe after the joint has been broken. The pipe gripping or slips section and the break-out section are both made in two halves each supported on an arm projecting from the respective platform so as to lie in the central plane of the machine, and means are provided so that at the appropriate times the two halves may be moved towards one another and locked together so as to become an operative whole, and at other times may be moved away from one another so that the drilling pipe and the pipe dismantling mechanism on the other lift may pass between them.

Of the pipe dismantling mechanism, the slips section is adapted to grip the pipe below a tool joint so as to take the load of the drilling string while pulling, the break-out section is adapted to grip the tool joint above and below the line of separation and the unscrewing means is adapted to grip the pipe above the tool joint for the purpose of unscrewing the end pipe section. It should perhaps be mentioned here that it is necessary for the break-out means to grip the tool joint itself and not the pipe so that the tool joint will be broken at the proper placeiotherwise there is a danger that one part of the tool joint will be unscrewed from the end of its pipe or that the pipe will be damaged.

The two ram pairs are arranged to operate over the same stroke, which is made a little longer than the longest pipe length. Each ram pair will then pull one section of pipe, break the joint and unscrew it ready for removal by the racking means (not yet described), while the other ram returns to the bottom of its working stroke ready to grip the n'extpipe joint, take over the pulling action and remove the next pipe section.

It will be appreciated that the process can only proceed in a smooth uninterrupted manner if the uppermost pipe sections are removed sufficiently rapidly to enable the pulling to proceed without a disconnected pipe fouling the rising drill string. Accordingly, means are provided for removing the pipe sections as they are dismantled and transporting them to storage space at the foot of the rig.

The entire rig is preferably assembled within a framework the main functions of which are as follows:

(1) To steady the rig and provide guiding rails for various vertically reciprocating parts.

(2) To support the pipe handling means which conveys the pipes to and from the string.

(3) To support ancillary gear, such as piping for carrying the drilling mud to the mud swivel during drilling operations, driving gear for rotating the pipe while drilling and so on.

The control mechanism whereby the various movements of the hydraulic lifting rams, pipe gripping and unscrewing mechanisms and the pipe handling mechanisms are all controlled is conveniently for the most part hydraulic in nature, although parts of it may with advantage be made electric and will include sensing means adapted to sense the arrival of a tool joint at a point accessible to the rig mechanisms, means to cause operation of the gripping means (slips) to cause them to grip the pipe at the correct location, and to cause operation of the break-out and unscrewing operations in the correct sequence and with the correct timing. Additionally the control mechanism will be required to control the operation of the pipe handling means so as always to present a holder for reception of the pipe section leaving the top of the drilling string. Other functions of the control mechanism will appear as the detailed description proceeds. Procedure when pulling pipe is as follows. Let us start with one lift, which will be called lift A, at the bottom of its stroke waiting to take over the pulling of the drill string. The other lift, lift B, is pulling the string, and when a tool joint approaches the gripping mechanism of lift A, the sensing device will operate, set lift A in motion, lift A will start to rise, quickly reaching the same velocity as the drill string, and its gripping mechanism will operate to grip the drill string a little below the tool joint which has just reached it. Shortly after this and when lift A has firmly taken hold of the string, lift B will approach the top of its travel and will release the top of the drill string. It now remains for the mechanism carried on lift A to break the newly emerged tool joint and spin off the top section of pipe while pulling the drill string, the whole operation being completed and the top section of pipe moved away from the path of the string by the time'lift A reaches the top of its stroke. The unscrewing action by which the top pipe section is removed from the string may be carried out either by mechanism associated with the lift as above described or mechanism may be provided for this purpose associated with the pipe handling mechanism. In either event, the pipe handling mechanism should be arranged to receive and support the topmost pipe section before disconnection is completed.

These operations being complete and lift A having nearly reached the top of its stroke, life B takes over at the next tool joint and lift A returns to the bottom of its stroke. This downward stroke takes place faster than the upward pulling stroke so that lift A will have reached its lowermost position before lift B has again reached the top of its stroke. This enables the mechanism to accommodate individual pipe sections which vary in length, since each lift will wait in its lowermost position until the next tool joint appears, and the time during which it waits will depend upon the length of the pipe section at that time emerging from the borehole. When the tool joint appears, the sensing device associated with the waiting lift starts operation of the gripping mechanism associated with that lift so that the next tool joint is gripped, broken out and the topmost pipe section spun off and removed.

When the drill collars at the end of the string are reached in the pulling operation, it may be preferred to stop the apparatus and proceed under manual control, the tools by which the string is handled being suitably modified to allow for the different diameter of the drill collars from that of the pipe or the tool joints. Alternatively the mechanism may be designed to operate effectively on the drill collars as well as on tool joints and to proceed automatically. To this end it may be necessary to provide at least one additional sensing device to sense the arrival of a drill collar joint as distinct from a pipe joint, one difference being that the joint between two drill collars lacks the shoulders which the tool joint makes when it gives place to pipe.

When running in pipe the operation as a whole is reversed. The one lift at the top of its stroke will fall, lowering the drill string into the hole, and the racking mechanism working in reverse will present a new pipe section for connection to the string. The second lift will wait at the top of its stroke for the top of the newly fixed pipe section to reach its gripping mechanism. A sensing device which may be, at least in part, the same sensing device as was used at the lower end to signal the arrival of the tool joint in the gripping mechanism, will respond to the approach to the gripping mechanism of the tool joint part on the upper end of the pipe and will cause the gripping mechanism to take a full load-carrying grip on the pipe immediately below the tool joint. Also the lift will be started on its downward journey and rapidly accelerated to the speed of the descending drill string. At the same time a new pipe section is presented to the gripping mechanism by the racking mechanism and the gripping mechanism associated with the lift will go through its operations of screwing on the new pipe section and tightening it up, using for this purpose the same mechanisms as were used for spinning off the pipe and breaking the tool joint respectively during the pulling-out operation.

During this running-in procedure the lifts are operated in a reverse way to that in which they are operated for pulling, that is to say they descend more slowly than they rise. In other words the unladen lift will rise to the top of its stroke in less time than it takes the laden lift to reach the bottom of its stroke, thus allowing the waiting time mentioned above. It will be understood that this waiting time will vary according to the length of the pipe section last added to the string.

For drilling purposes it is preferably arranged that either of the two lift mechanisms can be used, although it is not material from the point of view of saving time whether both lifts or only one can be used and it may be preferred for economy of equipment to arrange for only one of the two lifts to be applied to the drilling regime. Whichever lift is to be used for drilling will have attached to it as the need arises, a mud swivel, which term is used here to include the mechanism for rotating the drilling string and mechanism for introducing drilling mud.

The invention will be better understood from the following description of an example of a drilling rig according thereto given with reference to the accompanying drawings in which:

FIG. 1 is a front elevation of the complete rig omitting some of the framework;

FIG. 2 is a side elevation of the complete rig;

FIG. 3 is a rear elevation of the top of the rig;

FIG. 4 is a plan of the rig with some parts broken away showing the relative disposition of parts but omitting the lift platforms and mechanisms associated there with;

associated mechanisms of the rig at the passing positionj FIG. 7 is a plan view of a part of the slips mechanlsm;

FIG. 7a is a detail of the mechanism shown in FIG. 7;

FIG. 8 is an elevation of the part shown in FIG. 7;

FIG. 9 is a plan view of the platform mechanisms in the passing position but with the platforms and spin-off mechanisms removed;

FIG. is a side elevation of a set of platform mechanisms;

FIG. 11 is an end view of the racking trolley (i.e. a view from one side of the rig);

FIG. 12 is a rear view of the racking trolley and associated mechanisms;

FIG. 13 is a plan View of the racking trolley;

FIG. 14 is a diagram of the control equipment.

The general arrangement of the equipment is shown in FIGS. 14. The View shown in FIG. 1 is taken from what will for convenience be referred to as the front of the equipment, so that FIG. 2 becomes a side view and FIG. 3 a partial rear view. The equipment comprises a main framework 1 within which are the two pairs of hydraulic rams 2a, 2b and 3a, 317. These rams are located in the central plane of the main framework and straddle the bore hole which is, of course, at the center. Rearwardly of the main framework extends a subsidiary supporting frame 4 which serves to support the pipe racking mechanism by means of which pipes are removed from the drill string and transported to storage equipment on the ground. The framework 4 straddles a railway track 5 on which runs a trolley 6 in which the pipes are stored when not in the bore hole, as will be further described below. The outer pair of hydraulic rams 2a, 21) carries a platform 7 shown at the top of its stroke, while the inner pair of rams 3a, 3b carries a platform 8 shown at the bottom of its stroke. It will be observed that these platforms hang on stay rods from beams 17 supported on the tops of the hydraulic rams and are guided on vertical channel irons 32, 35 supported by the framework 1.

The platforms 7 and 3 carry mechanisms for gripping the pipe below a tool joint, breaking-out the tool joint and gripping the pipe above the tool joint for the purpose of unscrewing the topmost section. These mechanisms will be described in more detail later. At the top of the rig there is provided a railway 10 which serves to convey pipe sections to and from the center of the rig where they are removed from the pipe string or supplied to it for connection thereto. Hanging from the railway it are devices which will be termed hangers 11, each of which is adapted to receive a pipe section and hold it at appropriate times. There is a considerable number of these hangers, that is to say a number in excess of those required to hold pipe at any one time, and they circulate around the closed loop of rail 16) so as to be presented to various stations at appropriate times, as will hereinafter appear. One section 12 of the rail it hereinafter termed the 'batcher, is arranged to be separable from the remainder of the rail and is removable vertically on a lift carried by the subsidiary framework 4. The batcher serves to remove pipes from the rail 16 down to the trolley 6 in which they are stored when pipe is being pulled, and conversely raises pipes from the trolley 6 to the top of the rig when running-in pipe. The combination of the railway 19, the hangers 11 and the batcher 12 is referred to herein collectively as the pipe racking mechanism and its function will be described in detail later, but in general is as follows. Assume that drill pipe is being pulled out of the borehole and the batcher 12 is in position in line with the main rail 10. The batcher receives from the rig, along the railway, hangers 11, each of which is supporting a" pipe. When a complete batch of pipes has been built up in the batcher 12 the supply of pipes from the rail is held up by a catch, and the batcher 12 is lowered so as to bring the batch of pipes down into the trolley 6. At the bottom of the run, the hangers 11 are arranged to release the pipes automatically so that the batcher 12 can immediately be restored to its topmost position closing the gap in the rail 10. The empty hangers can now move from the batcher on to the rail to be replaced by further hangers carrying pipes which have accumulated at the end of the rail 10 on the rig side of the'gap into which the batcher 12 fits. The batcher 12 is thus again loaded and when the batch is complete it again descends to deposit this batch of pipes in the trolley 6. In the meantime the trolley 6 has been moved a short distance along the rails so that the new batch of pipes will be lowered into position alongside the previously deposited batch. The empty hangers are fed around the rail 19 and accumulate in a waiting location adjacent the central axis of the rig so as to be moved one at a time into position over the axis of the drill string to receive further lengths of pipe as they are pulled out from the borehole and dismantled from the drill string.

When running-in pipe, of course, the action is reversed, that is to say the batcher carrying a full batch of empty hangers descends to the trolley 6, picks up a batch of pipes, returns to the level of the rail 1% and its laden hangers are replaced by empty ones. The laden hangers are moved around the rail to a waiting station from which they are taken one at a time at the appropriate times and moved into position above the drill string so as to be available for addition to the drill string as required.

In the general arrangement shown in FIGS. 1-4, there is shown the driven swivel 14 which is vertically slidable on a square section or kelly drive shaft 13 which extends up one corner of the rig passing through platform 7 (FIG. 6). This carries the drive from motor 18 to the swivel which can be brought into action when drilling and stored above the throw of the platform 7 at other times. A lifting eye 19 may be used to support the swivel on a sling from the top of the rig when not in use. When drilling it is swung to the center of the rig and carried on either platform 7 or 8. The normal throw of the platforms 7 and 8 is limited at the lower end to a convenient height above ground level to provide the usual working space around the foot of the drill pipe for ancillary equipment, such as a blow-out preventer etc. shown at 9, forming no part of the present invention. Some additional space is also needed to allow for emergency override travel of the platforms for safety purposes when running-in. Some of this space may be employed when drilling to enable the stroke of the mud swivel to be increased below the normal level of the pulling stroke.

The various component parts of the rig according to the invention will now be described in detail in turn.

THE HYDRAULIC RAMS The rams 2a, 2b and 3a, 3b are all fundamentally alike and it will therefore be necessary only to describe one of them. FIG. 5 is a longitudinal sectional view, partly broken away, of a ram. It will be seen to comprise an outer cylinder 20, an inner cylinder 21 and a hollow piston rod 22 which operates in the space between them. An oil seal 23 carried by the upper end of the outer cylinder 29 seals the space between it and the outer surface of the piston rod at the top and oil seals 24 carried by the piston rod seal this space at the lower end of the piston. An inlet for pressure fluid is provided at 25 connecting with the enclosed space between the outer cylinder and the piston. A further oil seal 2% is provided at the upper end of the inner cylinder and .seals the space between the outside of the inner cylinder and the inside surface of the hollow piston rod, and the space between the inner cylinder and the inside of the hollow piston rod is fed withpressure fluid through an inlet 27. An additional fluid inlet 28 connects with the interior of the cylinder 21'. The dimensions of the various bores are chosen so that the effective areas of the hydraulic thrust surfaces: (a) on the lower end of the piston rod (the annular surface A), (b) on the inside of the piston rod through the cylinder 21 (the piston head B) and (c) on the outside of the piston rod (the annular surface C), are related in the ratio 4:2:1. It will be observed that the pressure exerted byv fluid introduced through inlet 25 operates downwardly on the piston rod While the other two pressures operate upwardly. It will now be seen that by the choice of different combinations of fluid supply, different thrusts can be achieved with the ram as follows:

Operative inlets Efiectivc thrust effective area) 27, 28 4+2=6 units. 25, 27, 28 4+21=5 units. 27 4:4 units. 27, 25--- 4-l=3 units.

8.. 2=2 units. 28, 2o. 2-1: 1 units. None Nil. 25. l=1 downwards.

PLATFORM MECHANISMS General A rrangement" The apparatus carried by the pulling-platforms 7 and Sis shown in FIGS. 6-10; FIG. 6' is a'plan view of the two platforms passing and PEG. 9 is a similar view, the section being taken, however, below the platforms proper so that the break-out mechanisms are shown; FIGS. 7, 7a and 8 give details of the slipsmechanism, while FIG. 10 is a side elevation of one complete platform mechanism. From the plan views the rear platform 8 is seen to be narrower than the front platform '7; This is because it isconvenient to match the sizes of. the platforms to the spacings between the respective pairs of rams from which they hang. The platforms are. steadied by the channels 32' and 35 provided on the main structure as above described. Platform 7 carries the axle 34 the ends of which carry wheels 31, running-in channels 32 and pinions 29 engaging racks il-provided'in the channels 32. This arrangement helpsto maintain the platform level. Similarly platform 8t carries axle 33bearing Wheels 34, running-in channels 35, and pinions running oil-racks in channels 35. Since the two'platform mechanisms are essentially alike it will be convenient to describe in detail only one of them. The main framework of platform 8 comprises apair of side members 36 and 37, between-which extendfcross members 33which support the platform proper; Betweenthe side members 36 and 37 extend bearer members 3 and dtlwhich support two trunnion arms 41. These extendinto the central plane of the rig and carry on trunnions at their ends the pipe gripping slips 42 (PEG. 10) and the break-out mechanisms 43 (FTGS. 6, 9 and 10*). The trunnion arms 4 are slidable towards and'away: from one another along the bearer members, being actuated by hydraulic rams 43 connected to the side members 36 and 3'7. The

slips 42 with the break-out mechanism mounted immediately above them at 43 are best shownin FIG. 10.

The platforms also carry the spinning-off mechanism. This mechanism grips the pipe above the tool joint and after the joint has been broken by the break-out mechanism, unscrews the top section, lifts it clear of the drill string, causes it to engage with one of the hangers of the pipe handling mechanism, and moves the lower end of the unscrewed pipe out of the line-of the rising drill string. This mechanism: comprises a pipe gripping and spinning unit 44 (FIG. 6), which will be described in greater detail later, which is mounted on a vertical spindie 45 upon which it can turn and also execute a rising and falling motion under the action of an actuating arm 46 powered by a hydraulic cylinder 47* (FIGS. 6 and 10).

In the above description and hereafter, the hydraulic cylinders referred to are all double-acting so that reference will be made simply to expanding and contracting them to'operate them inthe respective senses.

The Slips The slips 42 (FIG. 10) are required to grip the pipe below a tool joint sufiiciently firmly to take the Whole weight of the drill string and exerton it the necessary pulling force to withdraw it from-the borehole. As will have beenunderstood from the above description of the general arrangement, they are divided into two parts, each part being mounted on one of the trunnion arms, the two parts being brought together to'form an operative whole at the appropriate time in the machine cycle. FIG. 7 is a plan view and FIG/8a side view of one-half of the mechanism; The main-body or bowl Stl'is directly mounted on the trunnions 41 and'is provided with dowels 51' and dowel holes 52 by which it mates. with the other half when the two'halves are'brought together. Latching detents (not shown) are provided to lock the two halves in operative engagement during their operative phase. The grip on the pipe is provided by friction members'53 carried on slidingwedges 54-housedin channels 55 formed inthe main body 50. Above the wedges is provided a yoke member SSWhich is'in two halves, and each half is provided'with a dowel SE'aand a dowel hole 52:: (FIG. 8) for registration with its opposing half as in the case of the main body 5i). Latch means are provided to link together the two halves of the yoke. A lifting bar 6f connected to each wedge passes through a radial slot 62 in the yoke and spindles 6h carrying rollers 59 are provided passing through head members on the lifting bars one pair of rollers lying above and the other below the yoke 58 (FIG. 7a). It will now be seen that as the yoke is raiscd and lowered the wedges 54 will' rise and fall and the wedges will move radially,

' the radial movement being accommodated on the yoke 53' by the slots 62'and the rollers 59. The yoke o'fi'is raised and lowered by means of a piston 56-operating in a cylinder 57 connected with the main hydraulic fluid supply through control mechanism to be described later.

The operation of the slips will now be quite clear. When the slips are required to release the pipe, the yoke 58 will be lifted by the hydraulic piston 56, the wedges 54 thus being lifted and at the same time retracted'radially by the action of keys on the wedges sliding in keyways on the main bowl 50. When:a pipe is to be gripped, piston 56 will be drawn downwardly in its cylinder thus pulling the yoke 53 down, pulling the wedges downwardly in their grooves and so radially inwardly under the action of their inclined keys and keyways to grip the pipe.-

Clearly the weight of the pipe acting on the friction members 53 will tend to pull the wedges downwardly, thus increasing gripping on the pipe in the normal manner of wedge slips. FIG. 10 shows how the slips are mounted on their respective trunnions immediately below the break-out mechanism which will now be described.

The function of the break-out mechanism is to break the tool joint ready for unscrewing by the spinning-off mechanism. It is required to grip the two halves of a tool joint and unscrew the joint by a fraction of a turn. The tool joint will have been screwed up during the running in process to a standard tightness and may have become more tightly engaged through the torque exerted on the drill string for drilling purposes. The torque which the mechanism must exert on the tool joint, therefore, is considerable and may be greater for the breakout than is used for the tightening up action which it is required to exert during the running-in process when a new tool joint is assembled.

The mechanism is in effect divisible into four sections, two sections, an upper and a lower, being carried by each trunnion. One trunnion carries the main operating mechanism and pipe gripping elements adapted to engage around one side of a tool joint while the other trunnion carries pipe gripping elements for engagement around the other side of the tool joint, being operated by movements transferred from their opposite numbers. As in the case of the slips the parts carried on the respective trunnions are brought together when the trunnions come together, are located by interengaging dowels and dowel holes (not shown) and are then locked together by a latching device (not shown) so as thereafter to function as a single unit. For an understanding of the operation of the mechanism it will be convenient to ignore the fact that it is constructed in two halves and regard it as a single unit. The arrangement is shown in FIG. 9 which shows a unit in plan view on each of the two platforms, the unit on platform 7 being in its inoperative condition and opened up so as to permit passage past it of the unit on platform 8 which is shown in an operative condition which it occupies at one time during the course of a break-out or a tightening-up operation. The operative part-of the mechanism is shown in elevation in FIG. 10.

The upper and lower sections of each break-out unit are arranged to grip the upper and lower parts of the tool joint respectively like wrenches and the mechanism for effecting this gripping action is the same for each of the two sections. Looking therefore at the upper section, it comprises a main beam 65 and a locking arm 66, the extremities of which are linked by a hydraulic cylinder 67 pivoted at one end of the beam 65 and piston 67' pivoted to arm 66. This linkage functions to open out these arms to produce a locking action on the tool joint by means of cam actuated gripping dies 63. As will be seen from FIGS. 9 and 10, main beam 65 is provided with a cylindrical body portion which rests on and is supported by a similar cylindrical portion of main beam 76, and in which the gripping dies 63 are radially movable under the action of cam surfaces 64 formed in the inner surface of a surrounding cylindrical cam ring portion of arm on. Relative rotation of the die carrying body portion of beam 65 and the surrounding cam ring portion of arm 66 thus causes the gripping dies 63 to move radially inward into engagement wtih the tool joint. The lower section of the break-out mechanism, like the upper section, has a main beam 70 and locking arm 71 linked by the hydraulic cylinder 72 pivoted to beam 7% and piston 72 pivoted to arm 71. The cylindrical body portion of main beam 79 and the surrounding cam ring portion of arm 71 rest on and are supported by the superstructure or" the underlying part of the slips 42, while the outer end portion of beam 70 is also supported on trunnion 4:1, as indicated in FIG. 10. The locking function in the case of this lower section is precisely similar to that of the upper section and need not be described in detail.

The upper and lower sections are cross linked by a pair of hydraulic cylinders 73 and 74 and their associated pistons and when operated these devices swing the upper section relative to the lower section through an angle suiiicient to break the joint (or, in the reverse sense,

tighten it). The upper mechanism in FIG. 9 is shown in its operated condition. Arm 71 is shown spread from the beam 70 to lock the section on to the lower part of the tool joint. Arm 66 is spread from the beam 65 to lock the upper section on to the upper part of the tool joint, while the two beams 65 and 76 are shown swung out of line through an angle of approximately 45 which is sufficient to break the joint. In this position, of course, all the hydraulic cylinders are fully extended.

The sequence of operations through which the mechanism passes from the state shown in the lower part of FIG. 9 to the state shown in the upper part of FIG. 9 and back again will of course depend on whether the mechanism is being used to break out a joint (when pulling out) or to tighten a joint (when running in). The sequence when breaking a joint will be as follows:

spread arm 66 from beam 65 clamping the upper section onto the tool joint.

(1b) Cylinder 72 is expanded to spread arm 71 from beam 70.

These two operations may take place simultaneously.

(1a) Cylinder 67 is expanded to! (2) Cylinders 73 and '74 are expanded to swing the upper section anti-clockwise to break the joint, the lower section being held rigid (upper part of FIG. 9).

(3) Cylinders 67 and 72 are contracted to release the clamping action on the tool joint parts.

(4) Cylinders 73 and 74 are contracted to restore mechanism to the position shown in the lower part of FIG. 9.

For tightening up a joint the sequence is as follows:

SPINNING-()FF MECHANISM The spinning-off mechanism 44 can be seen in general outline in FIG. 2 in two conditions of operation. It is shown in more detail in FIG. 10 in elevation and in FIG. 6 in plan. It is mounted above the lift platform and comprises a unit for gripping and spinning the pipe above the broken tool joint, and mechanism for raising and lowering this unit.

The main unit comprises a body in the form of two plates 81, 82, the forward ends of which form upper and lower jaws 81a, 82a, which carry between them rollers 85, 86, for engagement with the pipe. There is also pro vided a movable jaw 83 carrying a third roller 34. The moving jaw is operated by a hydraulic cylinder and piston 87 to close it on to the pipe at the appropriate time. An electric motor 88 is coupled to the roller 86 to drive it and so apply a rotational drive to the pipe. This motor must of course be reversible so that it can apply either clockwise or anti-clockwise rotation to the pipe for screwing in or unscrewing the pipe section. The whole unit is mounted on the vertical-spindle 45 (previously referred to) on which it can swing through approximately a right angle from the position in which its jaws can engage a pipe of the drill string to a position over the platform where it is out of the way of the closed platform mechanisms of the other lift. This swinging motion is introduced by means of a further electric motor 90 which carries at its lower end a spur gear 91 which engages with a 11 fixed segmental rack (not visible in the drawings) mounted on the framework. Clearly this motor also must be reversible to provide for the two directions through which the unit is to be moved.

The whole of the unit above described is also movable vertically on the spindle 45 and its vertical movement is brought about by the double armed lever 46 fulcrurned at 94 (FIG. the outer end ofwhich is operated on by the hydraulic cylinder 47.

The functioning-of the spinning-off unit will now be clear. At the appropriate moment the unit is swung across and its jaws closed upon a pipe emerging from the bore hole just above the tool joint which has been engaged by the break-out: mechanism. The break-out mechanism having operated, the motor 88 spins the pipe anti-clockwise to'unscrew it, and as soon as it is clear the cylinder 47 is contracted to pull down the outer end of lever 46 and raise the spinning-elf unit. This lifting movement is relatively rapid and of course is superimposed on the rising motion of the lift platform so that the disconnected pipe will be thrust upwards into a waiting hanger. The movement of the disconnected pipe during this manoeuvre may require a fixed guide member to be provided to steady the pipe and guide it towards the hanger with which it is to be engaged. Thereupon the spinning-off unit is swung aside by the motor 30 carrying with it the lower end of the disconnected pipe. At the same time the hanger carrying the pipe is moved off around the railway 10 and thus the dismantled-pipe is got clear of the rising drill string, pulling of which is about to be taken over by the lower lift which is waiting for the next tool joint to arrive. Similarly the swinging sideways of the spinning-off serves to remove it from the central area of the rig altogether so that the lift with which it is associated may pass downwardly andallow the other lift to pass up carrying with it the drill string. During the passage downwards of the lift, the cylinder 47 is expanded to return the spinning mechanism to its lower position ready for the next operation.

PIPE RACKING MECHANISMS The Hangers A hanger comprises a tubular box of large enough internal cross section to receive the part. of the tool joint carried on the upper end of a pipe to be thrust into it. The lower end of the tube may be flared in order to allow for some variation of the actual position of the upper end of a pipe when it reaches the hanger. The length of the hanger must moreover be enough to accommodate the variations in length of pipe which are encountered in practice. It will be appreciated that the spinning-off mechanism will at all times grip a pipe section at substantially the same distance above the tool joint so that when the pipe section is delivered into the charge of a hanger the lower end of the pipe will always be at substantially the same level. It follows that the position of the upper end of the pipe will vary according to the length of the pipe section. This is convenient, as will appear below, since it follows that the lower ends of the pipes as they hang in their hangers will lie in a common plane so that when they are lowered to the storage trolley 6 at the foot of the rig they will reach the floor of the trolley simultaneously and be set down together. Details of the hanger are shown in FIG. 3. The outer box structure 100 is shown broken away to reveal the gripping cams 101 on one side of the box. The cams are provided in pairs facing'one another. They are pivoted as shown at 102 so that their inner ends may be pushed upwardly by the tool joint on the end of a pipe entering the hanger and Will'fall back against the pipe when the tool joint has passed so as to grip the pipe with a wedging action when the weight of the pipe begins to act downwardly on them. Their grip on the pipe may be made positive by serrating the cam faces or lining them with friction material. The outer ends of the cams are linked together by rod 103 which extends up through the casing to emerge at the top at 104. This provides for the release of the pipe by ancillary mechanisms at the appropriate times. A downward pressure on this rod end tilts the cams upwardly, so releasing them from the pipe. This rod will be actuated byv a releasing bar when the pipes are lowered into the racking trolley at the bottom of the rig as pipes are returned to storage during the pulling-out operation. When runningin the rod 103 will ride under and so be pushed down by a cam 99 on the underside of rail'107 at the top of the rig as the pipe is swung by the screwing-in mechanism.

(the spinning-off mechanism for pulling-out) into position over the drill string to which it is to be added.

The hanger is supported on an arm 105 which carries a pulley 105 which runs on the rail 107 which is part of the railway structure indicatedgenerally by the reference numeral 10 (FIGS. 3 and 4).

The suspension arm 105 also carries an upstanding finger 198 by which the hanger is moved along the railway. This finger is engaged by fingers-109 carried'on an endless moving chain associated with the railway 10. The finger 108 is spring loaded into the driving position in which it engages the fingers 109 by any suitable means (not shown). The purpose of this is to facilitate controlof the hangers in their movements along the. railway.

The introduction of a positive stop checking the move-- ment of hanger results in the spring loading of the finger being overridden so that the chain 110 may move on,

' leaving the hanger in the position in which it has been restrained.

A group of eight hangers nested together on the batcher is shown in plan in FIG. 4.

The Butcher The batcher is shown in side elevation in FIG. 3' and in plan in FIG. 4. his also indicated generally in FIG.

2. It'consists merely of a framework 111 disposedin avertical plane and is guided by wheels 112 runningin vertical channel ways 113 sothat it may be raised and lowered between the top andbottom of the rig. The channel ways 113 form part of the auxiliary structure indicated" generally at 4in FIG. 2. At its upper end the frame 111' is provided with a-truss-like extension'lll (FIG; 3)' having secured thereto a bracket 115 which carries a section of rail-116 which, when the batcher is-in'its topmost posi tion fits into a gap in the rail'107'so as to complete the closed loop of railway 10. Hangers running on rail 107' can therefore be pushed by the chain 110 onto or off from together side by side. on the frameworkon each side of the batcher. operated by the control mechanism as follows. One of them holds up the flow of hangers past the batcher until a batch of eight has been collected in the batcher. other operates when the batcher is full to hold up the flow of hangers to the batcher while the batcher lowers its batch of pipes to the storage trolley and return to the position shown. This is of course when pulling pipe. When running-in the operation is reversed. As will be seen in FIG. 2, the batcher is raised and lowered by a cable 117 which passes up to a pulley 118 at the top of the rig, over the pulley and down to a hydraulic jigger 119.

The Railway This is the railway associated with the top of the rig for conveyingpipe hangers to and from the batcher, and- The sides which extend rearwardly right across the track on which runs the storage trolley, the loop being completed by the fourth side which constitutes the rearmost part of the rig. The nature of the railway has already been described in some detail with reference to FIG. 3. It consists of a channel-shaped way, the lower flange of which carries the rail proper 107, while the endless chain lltl previously referred to above is housed in a subsidiary channel above the rail. The chain is driven continuously by a driving motor 114 located at a rear corner of the rig (FIG. 4). As will be seen from the section of chain shown in detail within the batcher in FIG. 3, drive fingers are provided at closely spaced intervals on the chain. In addition it is to be understood that the railway carries a number of hangers considerably in excess of those actually in use at any one time. This is so that it may be certain that there will at all times be a reserve of empty hangers waiting to receive pipes as they emerge during the pulling-out operation and so that there will always be a reserve of empty hangers to fill the batcher before it descends to the pipe store and returns with a fresh load of pipes when running-in.

Pipe Storage At the foot of the subsidiary structure there is provided the racking trolley 6, which runs on track 121 (F163. 11 and 12). The trolley, on its track, can pass through framework 4- so as to pass directly under the batcher and is adapted to receive pipes standing in vertical attitude in closely packed form as seen in plan in FIG. 13. The pipes are delivered to the trolley in batches of eight, each batch constituting one row of the storage assembly. The floor of the trolley is preferably lined with wood or other relatively soft material so as to avoid damage to the pipe ends when they are lowered into it. Preferably also the floor of the trolley is profiled with corrugations as shown at 113 in the drawing to provide locations for the ends of the pipes. Successive rows of pipe are staggered crosswise of the trolley as shown so as to economize space. This staggering can readily be achieved by stopping the batch of hangers on the batcher alternately in each of the two positions required for the pipes to nest as shown.

So that successive rows of pipe may be set down in their correct positions, the trolley is inched forward in rhythm with the operation of the batcher. The mechanism for moving the trolley is indicated as comprising two racks 123 on each side of the trolley, one at the top and one at the bottom, engaging pinions 12 i fixed on the framework. The top and bottom pinions are operated by chain wheels 1225 linked by drive chains 126.

It is of course preferred to stack the pipes as closely together as possible, but as each batch of pipes is lowered into the store the pipes are supported in hangers and it is necessary to provide clearance between the new batch of pipes and those already in the store to accommodate the extra cross section of the hangers. When the hangers are withdrawn, of course, this clearance is no longer required. In order to provide this clearance without waste of space therefore, it is arranged that each batch of pipes is set down in a vertical attitude and is laid back against the previously stored pipes so as to be well clear of the hangers when next they arrive. This action is achieved by providing pipe separators 127 between each row of pipes. These pipe separators are bars bent to a wave profile, as will be seen from the plan view in FIG. 13, so as to provide notches each of which may receive a pipe. These bars are supported at their two ends on rails 128 on the trolley sides and terminate in cam follower projections 12). The cam followers 129 are operated on by a cam 13%) which is arranged to operate in rhythm with the trolley-moving rack and the batcher in the following way. Assuming that pipe is being loaded into the trolley and that the pipe shown at 131 is in the row last deposited, the pipe separator 127A will lie against it and separator 1273 will be some distance away from it. The descending pipes will demand vertically between the two separators 127A and 1273. The cam 130 then descends and engages in its right-hand straight groove 134 the cam follower on separator 127A and moves it to the left, as seen in the drawing, thus bringing the separator into contact with the newly-arrived pipes. Simultaneously the cam follower on separator 127B will be engaged by the left-hand branch of the inverted V-shaped groove 135 of cam 130 and will be moved to the right, as seen in the drawing, so that eparator 1 7B is brought into contact with the newly arrived pipes. The pipes are thus held between the two separators 127A and 127B. When the hangers have been withdrawn, the cam 13th moves upwardly again, the cam follower on separator 127A returning down the right-hand straight groove 1314 of the cam while the cam follower on pipe separator 127B follows the righthand leg of the V-shaped cam groove 135 so that the two separators 127A and 1273 will in fact move together towards the right and lay the pipes back parallel to those already stored. The Vertical reciprocating motion of the cam 130 produced by cylinder 133 in common with the vertical movement of racks 132 which operate upon the wheels 122, which drive the wheels 125 through a reversible ratchet, to inch the trolley along so that the trolley is automatically positioned ready to receive the next row of pipes, and the cam followers on pipe separator 127B and the next in sequence 127C will be positioned under the appropriate grooves of cam 13% for the next operation to take place. Clearly these operations will take place in reverse when pipe is being unloaded and supplied to the rig for runningin. In order that the trolley 6 shall move in the proper direction the drive between wheels 125 and pinions 124 is in the form of a ratchet which is reversible so as to provide reverse movement when running in from that required when pulling out.

THE CONTROL EQUIPMENT General The control equipment is required to coordinate all the operations of the rig and can be broken down into main control items and subsidiary control items. For example, the reversal of the rams from lifting to lowering and vice versa during pulling-out and running-in operations constitute items in an overall cycle of operation which involves the main hydraulic power unit. Co-ordinated with these items are the successive operations carried out by the break-out mechanism, the slips Wedges, the spinning-off mechanism and the hangers, each of which involves control of a minor cycle of operations which must be co-ordinated in itself as well as being fitted into the main cycle. g

In this specification no attempt has been made to describe in detail the various sensing devices which must be employed to co-ordinate the movements of the equip ment. They may indeed take a variety of forms such as micro-switches arranged to be actuated mechanically by the event it is required to sense and arranged when actuated to energise an electrically operated hydraulic control valve. In some circumstances, however, as will appear, the controlled element is an electric motor, in which case of course the control switch can operate, if necessary, through a relay to complete the circut of the motor.

It will be convenient to consider the main operating cycle of the two lifts and the control equipment therefor separately from the control of the minor cycles in which the subsidiary mechanisms operate, the co-ordination of the minor cycles within themselves and with one another being discussed later. V

The Main Lift Cycle It happens that whether the rig is pulling-out a pipe when running in being the direct reverse of the sequence when-pulling out. This task concerns in efiect only the unladen lift which is either returning to the bottom of its stroke to take a new pull or rising to the top of the rig,.unladen ready to lower the string by another pipe length. In either event the lift which is carrying the load either up or down is subject to a steady application of power or a steadily controlled relaxation, and no variations are required in its operation until the other lift takes over the load and what-was the laden lift becomes the unladen'lift. Accordingly the following description given with reference to FIG. 14 will consider the control exercised upon the unladen lift and will deal first with the process of pulling out.

As soon as a rising-lift-is relieved of its load as it nears the top of its stroke it becomes the unladen lift and it must go through the following cycle of operations:

When operation (7) is complete, i.e. when the lift has reached pipe speed, it is caused to take the load by actuation of its pipe gripping and break-out mechanisms and it ceases to be the'unl-aden lift; At this point the control apparatus transfers its attention to the other lift to carry it throughthe same cycle of operations. It follows that operation (7) on one lift gives place to operation (1) on the other, and since both of these operations employ the same setting ofthe lift control equipment they may be regarded as two parts of the same operation.

Looking now at FIG. 14 the four main rams are shown each with its three parts communicating with (A) The bottom of the piston,

(B) The inner bore, and

(C) The annulus between the piston and the other cylinder.

These are as'described-with reference to FIG. 5. The inner pair of rams-3"a-and-3b have their various ports connected together in pairs sothat the two rams work in parallel, and similarly so have the outer pair of rams 2a and 2b. The various pairs of ports have been labeled in FIG. 14 as in the-above list with the prefix O for the outer pair oframs and the prefix T for the inner pair. Elsewhere'the prefix L has been used to indicate the port of aladen ram and the prefix U for an unladen ram. These prefixes, of course, refer in turn to the ports of either ram.

The changeover between the two pairs of rams is effected by a changeover valve designated generally at 159. It is operated by a hydraulic servo-cylinder 151 controlled by a pilot valve 152 operated electrically under control of the contacts 153a, 1531) at the appropriate time in the operating cycle as will hereinafter appear. The valve has three sections, 150a, 150i) and 1500, connected to the pairs of ports OB, IB, 0A, IA, and 0C, IC respectively. For simplicity of explanation the arrangement to be described provides for only two degrees of loading, light and heavy, not employingthe multiple=cylinder rams to provide six loadings as above suggested; Consequently the ports C are used exclusively for control of the unladen lift. The light and heavy loadings are provided for by selective use of the two sets of ports A and B for the heavy and light loading respectively.

Selection between light and heavy loads is carried out by valve 155 in its central and'left-hand positions respectively. Inits right-hand position this valve prepares the circuit for running-in pipe in-place of pulling and for this changeover it is also necessary to change valve 156.

16 These two valves are, of course; operable as circumstances demand and not in rhythm with the cycle of lift operations above set out.

The hydraulic system is a closed circuit system and destinations marked T indicate connections to the supply tank. Two pump supplies are provided, one designated MP is the pump system supplying the mainoperating fiow to the loaded rams operatingthe lifts. The other designated CP is a constant pressure supply and is employed for control operations of the unladen rams.

Valve 157 is the main sequencing valve which controls the rhythm of' the control system to: accelerate and-decelerate the unladen lift rams in accordance with the regime above stated. The unladen lift is driven by the CP supply operating through the B ports of the respective rams to raise the unladen lift'in the first phase of the unladen lift control sequence when pulling pipe. When running in pipe the main pump system is used to raise the unladen lift at high speed. At other times the unladen lift falls under its ownweightunder. control of a variable choke 153:: or 158k (according to whether it is running in or pulling out respectively). In addition, at certain times the CP supply is used, operating through ports C and therefore downwardly, to accelerate the descending lift to its downward speed. All these differentrequirements are met at the times when they arise by the operation of the. sequence valve 157, the actions of which are given their appropriate significance according to whether pipe is being run in or pulled out by suitable setting of valve 155.

Now assume that pipe is being pulled and that a heavy load is involved so that valve is in its left hand position.

the system when the next tool joint is sensed and the functions of the lifts are to be reversed will now be traced. It is convenient to start from-the point where the ch angeover valve 1% operates. This isbrought about by operation of contact 153a which is operated'by a signal from the slips carried by the other lift when they have operated to grip the pipe. Main pressure supply to IA is then cutoff and IB is connected to UB and 1C to UC. It is the inner pair of rams in which we are now interested since they are operating the unladen lift.

At this point C? is connected. through 156a and 157a (position i) to U3, and this pressure maintains the inner lift rising at the speed of the string. This covers the period while the gripping mechanisms associated with that lift are releasing the string. UC is meanwhile connected to tank through 15712 (position 1) and 1560. Sequence switch 157 then moves to position 2. In this position CP is still connected to U3 and UC is connected to tank. The rams enter the buffers at the top of their stroke and are arrested.

Sequence switch 157 then moves to position 3. In this position UB is connected through 157a and 15617 and through variable choke 1581) to tank so that the inner rams 13 can start to fall. UC is still connected to tank.

Sequence switch then moves to position 4. In this position U0 is connected through 15711 and 1560 to CF and this provides downward boost to accelerate the inner lift downwards.

When the lift nears the bottom CP is cut off from UC by sequence switch 157 moving to position 5 leaving UB still connected to tank through 15611 and 15811.

The inner lift comes to rest and sequence switch moves to position 6. In this position UC is still connected to tank but U3 is cut off at 157a. The system waits in this The main pulling effort will be exerted then by connection of the main pump supply through valves It follows that OB is coupled to UBand 1C t'o LC. The operation of condition until the next pipe joint is sensed, whereupon sequence switch 157 moves to position 1 again, in which position CP is applied to, UB and the lift is accelerated to the speed of the string and its gripping mechanism applies itself to the tool joint. Once the slips have taken their grip they supply a signal to operate the changeover valve 150 and thereafter the process is repeated with the outer lift in the role of unladen lift.

Inspection of the drawing will show that when running in the same cycle of operations takes place but with certain functions reversed so that the cycle of the unladen lift, starting where the other lift takes over near the bottom of stroke, is as follows:

( l) Continues to move downward, slightly exceeding pipe speed so that the slip wedges can be raised.

(2) Decelerates to rest.

(3) Accelerated to twice pipe speed upwards (using main pumps).

(4) Runs at twice pipe speed.

(5) Slows to rest.

(6) Waits for next pipe.

(7) Accelerates downward to pipe speed and takes over.

It will be seen that this is the same pattern of operations as was listed for pulling-out and in the same way operations (1) and (7) merge the one into the other and may be regarded as part of the same operation. They both take place with the sequence switch 157 in position 1 and could be regarded as operations in and lb.

When running in the operative lift (is. the lift on which the string hangs) is supplying pressure fluid back to tank. The operative lift is therefore connected'to tank through two power absorbing units (PAU). These may take any convenient form such, for example, as flow-restricting valves and radiators for dissipating the heat generated by the fluid flow.

The operations of the sequence switch 157 are brought about electrically by signals derived from a plurality of sensing devices (only two of which indicated as switches i8 operation to be controlled thereby and for the speed of travel of the lift at the time. It will probably be preferred to provide separate sets of switches for control of the running in and pulling out sequences, the appropriate set being b'rought'into action at the respective times as will be readily understood.

It will also be appreciated that in the hydraulic system above described normal additions such as air accumulators and such like have been omitted since they form no part of the present invention. Additionally, in the control equipment above described as well as in the control of the subsidiary equipments yet to be described suitable interlocks and cutouts will be provided to ensure against operation of the various parts in the wrong order and against damage to the apparatus in the event of failure of any part of it to operate is intended.

The Lift Mechanisms The operations of the lift mechanisms, i.e. the slips, the break-out tongs, the spin-off mechanism and mechanism for bringing together the two separable parts of the lift mechanisms, are so closely interwoven that it is best to consider them under one heading. Most of the operations involved are dependent one upon another and will be trigsered off y t e p ion of he p eced n e at n- Since each operating circuit amounts to no more than a trigger operated by the appropriate event and a solenoid or other actuating device energised hy the trigger, it is not necessary to draw the circuits involved. What is important, however, is to set down the time sequence governing the various opena-tions.

In the following table the sequence is given for the pulling out process, time progressing downwardly, the events in the column labelled operation to the right Of the table overlapping with those written at the same level in the column similarly labelled at the left of the table. The arrows indicate that the event at the tip of the arrow is triggered by the event at the tail of the arrow or by the successful completion of the earlier event.

PULLING OUT Primary event Operation Actuating Operation Actuating device device Lifts pass (relevant lift going down) Trulmion arms 41 close .s 48

Block halves late h together Lift mechanism moving with tool joint Slip wedges actuate 56, 57-) Slips on other lift disengage (going up). Break-out mechanism locks 0m... 62, 72 Spin-0E mechanism swings in 90, 91 Break-out mechanism actuates 73, 74 Spin-off mechani'sm clamps 87 Break-out mechanism unlocks-.." 62, 72 Spin-off motor starts 88 Break-out mechanism retracts 73,74 Spin-otffipotor stops and mecha- 83 nisrn 1 s. Lift nears top of stroke- Spin-off mechanism swings aside 90, 91 Hanger moves with pipe .c Slips on other lift engage. Slip wedges withdraw 56, 57 Lift reaches top of travel. Spin-oft mechanism releases pipe 87 Block halves uxllateh Trunnion arms separate 48 159a, 15% are shown) suitably located on the rig. In order to avoid having relatively vulnerable switches exposed to the rigors of rig conditions the rig may be provided with remote indicating equipment to reproduce the movements of the lifts on a reduced scale in the control cabin which will normally be provided. Micro switches arranged on this simulator are then operated mechanically by the simulated movements of the lifts so as to take place at suitable times in relation to the positions and movements of these lifts. Naturally, allowance will have to be made in the settings of these switches for the time lag between operation of the switch and fulfilment of the From the above it will be seen that the trunnion arms 41 can start to close upon one another just so soon as the platforms have passed one another, since the pipe and tool joints can pass between them. They are therefore closed and latched together on the downward journey so as to be ready and waiting for the next tool joint to reach the bottom of the lift stroke. The timing of the operations of the spinning-off mechanism in relation to the breakout mechanism is not critical; the spinning-off will not take place until the joint has been broken, but it is preferred to have the mechanism ready to spin the pipe just so soon as it is free. 

7. IN AN EARTH DRILLING RIG, THE COMBINATION OF AT LEAST TWO LIFTS EACH TRAVERSABLE IN OPPOSITE DIRECTIONS ALONG THE DRILLING AXIS OF THE RIG FOR RAISING AND LOWERING A DRILL PIPE STRING, PIPE ENGAGING MEANS CARRIED BY EACH OF SAID LIFTS, EACH OF SAID PIPE ENGAGING MEANS BEING COMPOSED OF TWO SECTIONS, MEANS FOR MOUNTING SAID SECTIONS ON THE ASSOCIATED LIFT FOR MOVEMENT TOWARDS AND AWAY FROM ONE ANOTHER, MEANS FOR BRINGING THE SECTIONS OF ONE OF SAID PIPE ENGAGING MEANS TOGETHER ABOUT THE DRILLING AXIS WHILE THE ONE ASSOCIATED LIFT IS TRAVERSED IN ONE DIRECTION ALONG THE DRILLING AXIS, AND MEANS FOR SEPARATING THE SECTIONS OF THE OTHER OF SAID PIPE ENGAGING MEANS AND REMOVING THEM 